Hybrid inflator

ABSTRACT

A hybrid inflator in which a weight thereof and the number of manufacturing steps can be reduced is provided. First and second communication holes 125 and 135 by which first and second gas generating chambers 120 and 130 communicates with an inflator housing 102 are formed in a gas generator housing 105. Therefore, no screen is required and thus, the weight and the number of manufacturing steps can be reduced.

This application claims on U.S. Ser. No. 09/680,431 filed on Oct. 6,2000, U.S. Pat. No. 6,488,310, under 35 U.S.C. § 120, and JapaneseApplication Nos. 2000-89391 filed on Mar. 28, 2003 and 2001-69635 filedon Mar. 13, 2001 under § 119.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP01/02480 which has an Internationalfiling date of Mar. 27, 2001, which designated the United States ofAmerica.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inflating-type safety system for amotor vehicle, more specifically to a hybrid inflator capable ofinflating an air bag reliably and rapidly, and to an air bag systemusing the hybrid inflator.

2. Description of Related Art

With the development of an inflator for an inflating-type safety systemof motor vehicles, a hybrid inflator using both a pressurized gas and asolid gas generating agent has been attracting attention. A main designrequirement for a hybrid inflator is that the inflator inflates an airbag to a predetermined amount in a predetermined period of time so thatthe air bag is effectively activated. Various proposals concerning astructure to meet the requirement have heretofore been made (forexample, as referred in JP-A 8-282427). Since such a hybrid inflator ismanufactured to be installed in a motor vehicle, the weight anddimensions of the inflator, which have influence upon the weight of themotor vehicle, constitute an important design requirement therefore.Moreover, it is required to reduce the weight and number of parts whilemaintaining function as the hybrid inflator.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a hybrid inflator inwhich a weight of the inflator can be reduced and manufacturing processcan be simplified, and to provide an air bag system using such a hybridinflator.

A hybrid inflator of the present invention can be applied to any of asingle type hybrid inflator having a single gas generating chamber and amultistage inflating hybrid inflator having two (dual type) or more thanthree gas generating chambers.

The present invention provides, as one means for solving the aboveproblem, a hybrid inflator for an inflating-type safety system of avehicle provided with an air bag, which comprises an inflator housing, agas generator provided in the inflator housing, and an ignition meanschamber having ignition means joined to the gas generator, wherein

the interior of the inflator housing is filled with a pressurized mediumcontaining an inert gas,

the gas generator has an outer shell formed by a gas generator housinghaving a plurality of communication holes, the gas generator includes,in the gas generator housing, a gas generating chamber whichaccommodates a gas generating agent, the gas generating chamber and theinflator housing are in communication with each other through thecommunication holes,

each of the communication holes provided in the gas generator housinghas such a size that combustion gas generated in the gas generatingchamber can flow out there through but the gas generating agent can beprevented from falling outside.

This hybrid inflator is of a single type having one gas generatingchamber. It is possible to prevent the gas generating agent from fallingoutside without using a blocking screen by adjusting the size (holediameter) of the plurality of communication holes. Since the screen forcovering the communication holes by which the inflator housingcommunicates with the gas generating chamber provided in the gasgenerator housing is not used, the weight of the hybrid inflator can bereduced by the weight of the screen. Further, since a step for mountingthe screen is unnecessary, the number of manufacturing steps can bereduced, and the manufacturing step can be simplified.

Further, as another mean for solving the above problem, the presentinvention provides a hybrid inflator for an inflating-type safety systemof a vehicle provided with an air bag, which comprises an inflatorhousing, a gas generator provided in the inflator housing, and anignition means chamber having ignition means connected to the gasgenerator, wherein

the interior of the inflator housing is filled with a pressurized mediumcontaining an inert gas,

the gas generator has an outer shell formed by a gas generator housingwith a plurality of the first and second communication holes,

the gas generator housing includes, therein, first and second gasgenerating chambers each having a gas generating agent, the first gasgenerating chamber and the inflator housing are in communication witheach other through first communication holes, the second gas generatingchamber and the inflator housing are in communication with each otherthrough second communication holes,

each of the first and/or second communication holes has such a size thatcombustion gas generated in the first and/or second gas generatingchamber can flow out there through but the gas generating agent can beprevented from falling outside.

In the present invention, the following three modes may be employed: (a)the plurality of first communication holes are not covered with thescreen, but the plurality of second communication holes are covered withthe screen, (b) the first communication holes are covered with thescreen, but the second communication holes are not covered with thescreen, and (c) both the first and second communication holes are notcovered with the screen. Among these embodiments, (c) is mostpreferable.

This hybrid inflator is of a dual-type having two gas generatingchambers. Like in the above-described single type hybrid inflator, it ispossible to prevent the gas generating agent from falling outside byadjusting a size (hole diameter) of the first and second communicationholes without using a screen. Since the screen for covering theplurality of communication holes by which the inflator housingcommunicates with the gas generating chambers provided in the gasgenerator housing is not used, a weight of the hybrid inflator can bereduced by the weight of the screen. Further, since a mounting step ofthe screen can be omitted, the number of manufacturing steps can bereduced, and thereby, the manufacturing step can be simplified. In aconventional dual-type hybrid inflator, a screen is mounted to each ofthe first and second communication holes. Since the screens are notused, the number of parts can be reduced by two, and since the mountingstep of the two screens can be omitted, effects of reducing a weight andsimplifying manufacturing steps are extremely great.

In the hybrid inflator of the present invention, the plurality ofcommunication holes or the plurality of first and second communicationholes provided in the gas generator housing can have the same diameters.By setting the hole diameters of the communication holes the same, itbecomes easy to control the amount of outflow and the outflow state ofcombustion gas generated by burning the gas generating agent, andadditionally, manufacture of the gas generator housing can befacilitated.

In the hybrid inflator of the present invention, the plurality ofcommunication holes or the plurality of first and second communicationholes provided in the gas generator housing may have diameters in arange of 0.5 to 3 mm, more preferably in a range of 1.0 to 2.0 mm. Bysetting the diameter of each of the plurality of communication holes orthe plurality of first and second communication holes in thepredetermined range, the amount of outflow and the outflow-state of acombustion gas generated by combustion of the gas generating agent canbe controlled in the communication holes, as a whole, even when some ofthe holes are clogged.

Further, in the hybrid inflator of the present invention, the totalnumber of the communication holes or the first and second communicationholes provided in the gas generator housing may be 100 to 600, morepreferably 200 to 500. By setting the total number of the communicationholes or the first and second communication holes in a predeterminedrange, the amount of outflow and the outflow-state of a combustion gasgenerated by combustion of the gas generating agent can be controlled inthe communication holes, as a whole, even when some of the holes areclogged.

Further, in the dual-type hybrid inflator of the present invention, thetotal number of the first communication holes may be 50 to 300, morepreferably 100 to 250, and the total number of the second communicationholes may be 50 to 300, more preferably 100 to 250. By setting the totalnumber of the first and second communication holes in a predeterminedrange, the amount of outflow and the outflow-state of a combustion gasgenerated by combustion of the gas generating agent can be controlled inthe communication holes, as a whole, even when some of the holes areclogged.

Further, in the hybrid inflator of the present invention, the total openarea of the communication holes or the first and second communicationholes provided in the gas generator housing may be 100 to 600 mm², morepreferable 200 to 500 mm². By setting the total open area of thecommunication holes or the first and second communication holes in thepredetermined range, the amount of outflow and the outflow-state of acombustion gas generated by combustion of the gas generating agent canbe controlled in the communication holes, as a whole, even when some ofthe holes are clogged.

Further, in the hybrid inflator of the present invention, the pluralityof communication holes or the plurality of first and secondcommunication holes provided in the gas generator housing may bearranged in a plurality of lines in the longitudinal direction of thegas generator housing as well as in a plurality of lines in the outerperipheral direction. By arranging the communication holes in theplurality of lines, requirements concerning the hole diameter, the totalnumber and the opening area of the communication holes can be controlledeasily, and thereby, the hybrid inflator which fulfills the requirementscan be produced efficiently.

Further, as another mean for solving the above problem, the presentinvention provides a hybrid inflator for an inflating-type safety systemof a vehicle provided with an air bag, which comprises an inflatorhousing, a gas generator provided in the inflator housing, and anignition means chamber having ignition means connected to the gasgenerator, wherein

the interior of the inflator housing is filled with a pressurized mediumcontaining an inert gas,

the gas generator has an outer shell formed by a gas generator housinghaving a plurality of first and second communication holes,

the gas generator housing includes, therein, first and second gasgenerating chambers each having a gas generating agent, a first ignitionmeans chamber having first ignition means is connected to a first gasgenerating chamber, a second ignition means chamber having a secondignition means is connected to a second gas generating chamber, thefirst gas generating chamber and the inflator housing are incommunication with each other through the plurality of firstcommunication holes, the second gas generating chamber and the inflatorhousing are in communication with each other through the plurality ofsecond communication holes,

each of the first and/or second communication holes has such a size thatcombustion gas generated in the first and second gas generating chamberscan flow out there through but the gas generating agent can be preventedfrom falling outside, the second communication holes are disposed at adistance from the second ignition means in the widthwise directionand/or the longitudinal direction of the inflator housing.

In this invention, the expression “the second communication holes aredisposed at a distance from the second ignition means in the widthwisedirection and/or the longitudinal direction of the inflator housing”includes three states from the second ignition means, i.e., a state inwhich the second communication holes are disposed at a distance in thewidthwise direction, a state in which the second communication holes aredisposed at a distance in the longitudinal direction, and a state inwhich the second communication holes are disposed at a distance in bothwidthwise and longitudinal directions. The widthwise direction of theinflator housing means a direction toward the side-walls of the inflatorhousing with respect to the center axis of the inflator housing in itslongitudinal direction.

When the second communication holes are disposed at a distance in thewidthwise direction of the inflator housing, it is preferable that allof the second communication holes are disposed in different directionsfrom the second ignition means in the widthwise direction of theinflator housing. When the communication holes are disposed in differentdirections in the widthwise direction of the inflator housing, it ispreferable that all of the second communication holes are directed to adirection different from the second ignition means through 90° orgreater in the widthwise direction.

In the hybrid inflator of the present invention, like in theabove-described single type hybrid inflator, it is possible to preventthe gas generating agent from falling outside by adjusting a size(diameter) of each of the first and/or second communication holeswithout using a blocking screen. Since such a screen can be omitted, theweight of the inflator can be reduced, the manufacturing step can besimplified, and falling of the gas generating agent can be prevented.With respect to relation between the first and second communicationholes and the screen, the above-described three modes, (a)–(c), can beemployed, and the mode (c) is most preferable.

In the hybrid inflator of the present invention, when the secondcommunication holes and the second ignition means are disposed close toeach other (i.e., when they are disposed such that the widthwisedirection of the inflator housing is the same direction as an examplethereof shown in FIG. 3, all the gas generating agent can be burnedsmoothly and uniformly by employing the above-described arrangement.Without the above arrangement, in general, the gas generating agent nearthe second communication holes is burned smoothly, but there is anadverse possibility such that gas generating agent away from the secondcommunication holes is not burned smoothly.

Further, the present invention includes the hybrid inflators of theabove-described inventions which are further provided with at least oneof the requirements selected among (1) to (3) described below:

(1) A molar ratio between an amount (A mol) of the pressurized mediumand an amount (B mol) of a gas generated due to combustion of the gasgenerating agent is 8/2 to 1/9;

(2) A weight ratio (X/Y) of the weight (X) of the pressurized medium tothe weight (Y) of the gas generating agent is 0.1 to 7; and.

(3) A pressure index determined by the following formula: rb=αP^(n)(wherein, rb: burning rate, α: coefficient, P: pressure, n: pressureindex), at combustion of the gas generating agent, is smaller than 0.8.

The pressure index (n) is obtained by two formulas, rb₁=αP₁ ^(n) andrb₂=αP₂ ^(n), after the burning rates rb₁ is measured in a tank at thepressure P₁ (70 kg/cm²) and the burning rates rb₂ is measured in a tankat the pressure P₂ (100 kg/cm²)

By meeting the requirements (1) and (2), a charged amount of thepressurized medium can be decreased. Consequently, even when the volumeof the housing is decreased (in other words, the length and/or the width(the diameter) of the housing is decreased), a charging pressure of thepressurized medium (=the internal pressure of the housing) is notincreased, but can be maintained the same as that before the volume isdecreased. Preferably, A/B is 8/2 to 3/7, and X/Y is 0.5 to 5.

By meeting the requirement (3), a burning rate at the initial combustionof the gas generating agent is controlled not to increase abruptly, andthereby the internal pressure of the housing increases only slightly.Therefore, even when the thickness of the housing is reduced, asatisfactory heat-resistance can be retained. In addition, the gasgenerating agent is burnt stably because the internal pressure of thehousing increases only slightly (in other words, the internal pressurechanges a little), so that the gas generating agent can be burntcompletely. Preferably, the pressure index (n) is 0.1 to 0.8, and morepreferably, 0.1 to 0.7.

The gas generating agent used in the hybrid inflator of the presentinvention is not specially limited, and one example thereof is describedbelow. In the hybrid inflator of the present invention, as describedin 1) and 2) below, a gas generating agent accommodated in one gasgenerating chamber for a single type hybrid inflator, or a first gasgenerating agent accommodated in the first gas generating chamber and asecond gas generating agent accommodated in the second gas generatingchamber for a dual type hybrid inflator can be determined based on arelation with composition of pressurized medium charged in the inflatorhousing.

1) the pressurized medium including oxygen:

When the pressurized medium includes oxygen and an inert gas such asargon, helium (nitrogen is also included in the inert gas in the presentinvention), etc., the oxygen works to convert carbon monoxide andhydrogen generated due to the combustion of a gas generating agent, as agas generating means, into carbon dioxide and vapor, while argon worksto promote the thermal expansion of the pressurized medium. It ispreferable to contain helium in the pressurized medium since the fallingof the pressurized medium can be detected easily, for the purpose ofpreventing distribution of the imperfect products. Concrete compositionsof the pressurized medium including oxygen are determined in accordancewith gas generating agent to be used and a kind thereof, and the contentof oxygen is preferably about 8 to 30 mol %. A charging pressure of thepressurized medium (=pressure in the inflator housing) is preferably10,000 to 70,000 kPa and more preferably, 30,000 to 60,000 kPa.

As the gas generating agent in the single type hybrid inflator and thedual type hybrid inflator, a gun propellant can be used for example. Asthe gun propellant, a single-base gun propellant, a double-base gunpropellant, and a triple-base gun propellant can be used. In addition,it is possible to use a gun propellant obtained by mixing a secondaryexplosive, a bonding agent, a plasticizer, and a stabilizer, and thelike, and molding the resultant mixture to a desired shape.

The secondary explosive can include hexahydrotrinitrotriazine (RDX),cyclotetramethylene tetranitramine (HMX), pentaerithritol tetranitrate(PETN), and triaminoguanidine nitrate (TAGN). For example, when a gasgenerating agent using RDX as a secondary explosive is burned in anoxygen-absent atmosphere under a pressure of 20,670 kPa and at acombustion temperature of 3348 K, a formed gas in a combustion gascomprises 33 mol % of nitrogen, 25 mol % of carbon monoxide, 23 mol % ofvapor, 8 mol % of carbon dioxide, and other gas components.

The bonding agent can include cellulose acetate, cellulose acetatebutylate, cellulose acetate propiolate, ethyl cellulose, polyvinylacetate, azide polymer, polybutadiene, polybutadiene hydride, andpolyurethane; the plasticizer can include trimethylolethane trinitrate,butantriol trinitrate, nitroglycerine, bis (2,2-dintropropyl)acetal/formal, glycidyl azide, acetyltriethl citrate, and the like; andthe stabilizer can include ethlcentralite, diphenylamine, andloesosinol.

A preferable ratio of the secondary explosive to the bonding agent,plasticizer and stabilizer is about 50 to 90 wt. % of secondaryexplosive to about 10 to 50 wt. % of bonding agent, plasticizer andstabilizer in all.

It is difficult in some cases to burn the gas generating agent of theabove-described composition under normal pressure. However, in thehybrid inflator according to the present invention, since the interiorthereof is maintained at a high pressure in advance, the gas generatingagents can be burned stably and smoothly.

2) the pressurized medium not including oxygen:

When the pressurized medium includes substantially an inert gas such asargon, helium (nitrogen is also included in the inert gas in the presentinvention), etc., and when the composition does not contain oxygen,argon works to promote the thermal expansion of the pressurized medium.It is preferable to contain helium in the pressurized medium since theleakage of the pressurized medium can be detected easily for the purposeof preventing distribution of the imperfect products. Further, it ispreferable that the pressurized medium does not contain oxygen. However,the pressurized medium can contain oxygen in order to improve acombustion of the gas generating agents. In that case, the amount ofadded oxygen is preferably not more than 10 mol %, and more preferably 5mol %. A charging pressure of the pressurized medium is preferably10,000 to 70,000 kPa and more preferably, 30,000 to 60,000 kPa.

As the gas generating agent accommodated in the single type hybridinflator and the dual type hybrid inflator, it is possible to use amaterial including fuel and oxidizer, or fuel, oxidizer and slag-formingagent which are mixed together with bonding agent if necessary andformed into a desired shape. If such a gas generating agent is used, agas generated by its combustion can be supplied together with thepressurized medium for developing the air bag. Especially when the gasgenerating agent including the slag-forming agent is used, the amount ofmist discharged from the inflator can be reduced.

Preferably, the fuel can be at least one of the materials selected froma group consisting of guanidine derivative such as nitroguanidine (NQ),guanidine nitrite (GN), guanidine carbonate, amino nitroguanicine, aminoguanidine nitrite, amino guanidine carbonate, diamino guanidine nitrite,diamino guanidine carbonate, and triamino guanidine nitrite. Further asthe fuel, at least one of the materials selected from a group comprisingtetrazole and tetrazole derivative can be used.

As oxidizer, at least one of the materials selected from a groupcomprising strontium nitrate, potassium nitrate, ammonium nitrate,potassium perchlorate, copper oxide, ferrous oxide, basic copper nitratecan be used. Preferable composition amount of oxidizer is 10 to 80 partsby weight, and more preferably, 20 to 50 parts by weight with respect to100 parts by weight of fuel.

Preferably, the slag-forming agent can be at least one of the materialsselected from a group consisting of acid clay, talc, bentonite,diatomaceous earth, kaolin, silica, alumina, sodium silicate, siliconnitride, silicon carbide, hydrotalsite, and a mixture thereof.Preferable composition amount of slag-forming agent is 0 to 50 parts byweight, and more preferably, 1 to 10 parts by weight with respect to 100parts by weight of fuel.

Preferably, the bonding agent can be one or two or more materialsselected from a group consisting of sodium salt of sodiumcarboxymethylcellulose, hydroxyethyl cellulose, starch, polyvinylalcohol, guar gum, microcrystal cellulose, polyacrylamide and calciumstearate. Preferable composition amount of the bonding agent is 0 to 30parts by weight, and more preferably, 3 to 10 parts by weight withrespect to 100 parts by weight of fuel.

When the pressurized medium and the gas generating agent having theabove-described compositions are used, it is preferable that a molarratio (A/B) between an amount (A mol) of the pressurized medium and anamount (B mol) of a gas generated due to combustion of the gasgenerating agent is adjusted to 8/2 to 1/9, and more preferably 8/2 to3/7.

As described above, the charging amount of the pressurized medium can bereduced by adjusting the molar ratio between the amount of pressurizedmedium charged in the hybrid inflator and the amount of a gas generatedby combustion of the gas generating agent. Therefore, even when thevolume of the inflator housing is reduced (i.e., even when the lengthand/or width (diameter) of the housing is reduced), it is possible tomaintain the pressure at the same level as that before the volume isreduced, without enhancing the charging pressure (internal pressure ofthe housing) of the pressurized medium. In the hybrid inflator of thepresent invention, the weight ratio (X/Y) of the weight (X) of thepressurized medium to the weight (Y) of the gas generating agent ispreferably 0.1 to 7, and more preferably 0.5 to 5.

In the above hybrid inflator, it is preferable that a pressure indexdetermined by the following formula: rb=αP^(n) (wherein, rb: burningrate, α: coefficient, P: pressure, n: pressure index), at the combustionof the gas generating agent, is smaller than 0.8. The pressure index (n)is preferably 0.1 to 0.8, and more preferably, 0.1 to 0.7. In this case,the pressure index (n) is obtained by being measured in accordance withthe method described in the above requirement (3).

When the pressure index (n) is set to a value smaller than 0.8 in thismanner, the burning rate at the initial stage of the combustion of thegas generating agent is restrained from increasing abruptly, whereby,increase of the pressure inside the housing is small. Accordingly, asufficient pressure resistance of the housing can be maintained even ifthe thickness of the housing is reduced. Further, since the increase ininternal pressure of the housing is small (i.e., a variation in theinternal pressure is small), the gas generating agent is burned stablyso that all the gas generating agent is burnt completely.

In the hybrid inflator of the present invention, as a relation betweenthe pressurized medium and the gas generating agent, the above-describedcombinations 1) and 2) may be employed, and the combination 2) is morepreferable.

Further, the present invention provides an air bag system comprisingactivation-signal outputting means including an impact sensor and acontrol unit, and a module case which accommodates the above-describedhybrid inflator and air bag.

In the present invention, the term “gas generator” is the one having agas generating performance to generate a high temperature combustion gasdue to combustion of the gas generating means (gas generating agent) inthe gas generator housing (gas generating chamber), thereby allowing thehigh temperature combustion gas to flow into the inflator housing. Thehybrid inflator includes the gas generator in its inflator housing, andthe term “inflator” is the one having a performance to flow outside, thepressurized medium existing inside of the inflator housing as well asoutside of the gas generator to inflate an object to be inflated such asan air bag by flowing a high temperature combustion gas from the gasgenerator into the housing. The term “hybrid” means a combination of thehigh temperature combustion gas generated by combustion of the gasgenerating agent and the pressurized medium.

In the hybrid inflator of the present invention, since the screen, forcovering the communication holes by which the inflator housingcommunicates with the gas generating chamber provided in the gasgenerator housing, is not used, the number of parts and manufacturingsteps can be reduced, and thereby the cost can be effectively reducedbecause of weight-reduction of the hybrid inflator and the facilitatedmanufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing one embodiment of ahybrid inflator of the present invention;

FIG. 2 is a schematic plan view of a gas generator housing in the hybridinflator shown in FIG. 1;

FIG. 3 is a schematic sectional view of a second gas generating chamberin the widthwise direction thereof shown in FIG. 1;

FIG. 4 is a schematic plan view of the gas generator housing of anotherembodiment of the hybrid inflator of the invention; and

FIG. 5 is a schematic plan view of the gas generator housing of anotherembodiment of the hybrid inflator of the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention will be explained in detail as follows withreference to the drawings showing embodiments of the invention.

FIG. 1 is a longitudinal sectional view showing one embodiment of a dualtype hybrid inflator 100 having two gas generating chambers, FIG. 2 is aschematic plan view of a gas generator housing shown in FIG. 1, and FIG.3 is a schematic sectional view of a second gas generating chamber takenalong the widthwise direction thereof shown in FIG. 1. FIGS. 2 and 3 areused for explaining layout of communication holes.

As shown in FIG. 1, an inflator housing 102 comprises a cylindricalpressure resisting container, and its inner space 103 is filled with apressurized medium and maintained at a high pressure. The pressurizedmedium is usually charged from a small hole 107 formed in a boss 145connected to one end of the inflator housing 102, and the small hole 107is closed with a seal pin 109 after the pressurized medium was charged.The inflator housing 102 can be formed to have an uniform outer diameterexcept its end portion on the side of a diffuser 180 (flat outer shapewithout constriction or the like).

An outer shell of a gas generator 108 includes a gas generator housing105. The gas generator housing 105 includes, therein, a flametransferring means chamber 110, and a first gas generating chamber 120and a second gas generating chamber 130 formed to surround the flametransferring means chamber 110 and disposed adjacent to each other inseries in the longitudinal direction of the inflator housing 102. Thegas generator 108 is disposed in the inflator housing 102, and its oneend in its longitudinal direction is fixed to the boss 145 by welding.

The flame transferring means chamber 110 comprises a cylindrical housing111, and is connected to a first igniter 117 through a booster cup 116 ain which a booster agent (transfer charge) 112 a is charged and a firstcommunication passage 113 closed by a first rupturable disc 119 as afirst closing means. The flame transferring means chamber 110 is incommunication with the first gas generating chamber 120 through flametransferring holes 118.

The first gas generating chamber 120 surrounds the flame transferringmeans chamber 110, and is defined by the gas generator housing 105, thehousing 111 of the flame transferring means chamber 110, a firstpartition wall (first retainer) 126 and a second partition wall (secondretainer) 136. A desired amount of a first gas generating agent 124 isaccommodated in the first gas generating chamber 120. The first gasgenerating chamber 120 and the inflator housing 102 are in communicationwith each other through a plurality of first communication holes 125.

As shown in FIG. 2, a plurality of first communication holes 125 aredisposed in six rows (six holes) in the longitudinal direction of thegas generator housing 105, and disposed on the entire surface of the gasgenerator housing 105 in the outer peripheral direction. The pluralityof first communication holes 125 are disposed in order as shown in FIG.2, but they can be disposed staggered in the same way as the secondcommunication holes 135.

A diameter of the first communication hole is 1.2 mm, and the totalnumber of the first communication holes is 192, and the total openingarea is 217 mm². The plurality of first communication holes 125 does nothave to be disposed on the entire surface in the outer peripheraldirection and may be disposed only on a portion of the surface.Alternatively, the holes may be divided into a plurality of groups andthe groups of the holes may be disposed separately at an appropriatedistance from one another. Being disposed on a plurality of surfacesmeans that, for example, a hundred and ninety-two first communicationholes 125 in total are divided into two groups of 96 holes, and thesetwo groups are disposed separately from each other. The firstcommunication holes can be divided into more than three groups and thesegroups can be disposed separately from each other.

In the hybrid inflator 100 of the present embodiment, since a screen forpreventing the first gas generating agent 124 from falling out is notprovided and thus, the first communication holes 125 and the first gasgenerating agent 124 are in contact with each other.

The second gas generating chamber 130 is defined by the gas generatorhousing 105, the housing 111 of the flame transferring means chamber110, the second partition wall (second retainer) 136, and the boss 145(and second rupturable disc 139). A desired amount of a second gasgenerating agent 134 is accommodated therein. The second gas generatingchamber 130 and the inflator housing 102 are in communication with eachother through the plurality of second communication holes 135.

The plurality of second communication holes 135 are disposed, forexample, as shown in FIG. 2, in the longitudinal direction of the gasgenerator housing 105 in four rows (four holes), and disposed on a halfof the surface of the gas generator housing 105 in its outer peripheraldirection (see FIG. 3). The plurality of second communication holes 135are disposed staggered as shown in FIG. 2, but they can be disposed inorder in the same way as the first communication holes 125.

A diameter of the second communication hole 135 is 1.2 mm, and the totalnumber of the second communication holes is 128, and the total openingarea is 145 mm². A plurality of the communication holes 135 may bedisposed only on a portion of the surface. Alternatively, as describedabove, the holes may be divided into a plurality of groups and thegroups of the holes may be disposed separately from one another.

In the hybrid inflator 100 of the present embodiment, since a screen forpreventing the second gas generating agent 134 from falling out is notprovided and thus, the second communication holes 135 and the second gasgenerating agent 134 are in contact with each other.

The second gas generating chamber 130 is connected to a second igniter140 through a second communication passage closed by the secondrupturable disc 139 as the second closing means. Reference number 112 brepresents a booster agent, and reference number 116 b represents abooster cup.

Since the first igniter 117 and the flame transferring means chamber 110are disposed on the center axis (shown with the chain line in FIG. 1,and with a center point O in FIG. 3) in the longitudinal direction ofthe inflator housing 102, the second igniter 140 is disposedeccentrically with respect to the center axis. Therefore, as shown inFIG. 3, the second gas generating chamber 130 is formed such that thesecond communication holes 135 are located on the opposite side of thesecond igniter 140 in the widthwise direction (radial direction). Whenthe second communication holes 135 and the second igniter 140 aredisposed close to each other, for example, (when the second igniter islocated at the position 140 a shown with the broken line in FIG. 3), thesecond communication holes 135 and the second igniter 140 a are disposedto be in the same direction in the widthwise direction of the inflator.Therefore, the gas generating agent 134 in the vicinity of the secondigniter 140 a can be burnt well, but the gas generating agent 134existing on the opposite side cannot be burnt enough.

FIGS. 1 to 3 show the dual type inflator having two gas generatingchambers. An example in which the present invention is applied to asingle type inflator having one gas generating chamber is shown in FIG.4. In the case of the single type hybrid inflator having a gas generatorhousing 205 shown in FIG. 4, a plurality of communication holes 225, bywhich the single gas generating chamber communicates with the inflatorhousing, are disposed in ten rows (ten holes) in the longitudinaldirection of the gas generator housing 205 and, at the same time,disposed on the entire surface thereof in the outer circumferentialdirection. A diameter of the communication hole 225 is 1.2 mm, and thetotal number of the communication holes is 320, and the total openingarea is 362 mm². In this case, the communication holes 225 do not haveto be disposed only on the entire surface in the outer peripheraldirection and may be disposed only on a portion of the surface.Alternatively, as described above, the holes may be divided into aplurality of groups and the groups of the holes may be disposedseparately from one another.

In the hybrid inflator 100 shown in FIG. 1, irrespective of whether ornot the second igniter 140 is disposed eccentrically, the firstcommunication holes 125 and the second communication holes 135 can beformed such that some or all of the holes are directed differently inthe widthwise direction of the inflator housing in order to prevent mistfrom discharging from the inflator housing 100.

Next, one embodiment of the layout of the first communication holes 125and second communication holes 135 will be explained based on FIG. 5. InFIG. 5, a surface of the gas generator housing 105 on the side of thesecond gas generating chamber 130 is cut out. In this case, “mist” inthe following corresponds to a solid component (for example, a metalcomponent) in the gas generating agents which is generated due tocombustion of the gas generating agents.

As shown in FIG. 5, a plurality of first communication holes 125 areformed only on one surface of the gas generator housing 105, and aplurality of second communication holes 135 are formed only on theopposite surface of the gas generator housing 105. By disposing thefirst communication holes 125 and the second communication holes 135 onthe widthwise-opposite sides, facing each other, of the surface of thegas generator housing 105, when a mist (first mist) generated by burningthe first gas generating agent 124 in the first gas generating chamber120 flows out from the first communication holes 125 and adheres to anopposite inner wall surface of the inflator housing 102, a gas flow(second gas flow) generated by combustion of the second gas generatingagent 134 in the second gas generating chamber 130 flows into theopposite side of the inner wall surface of the inflator housing 102 onwhich the first mist adheres. Therefore, the first mist is preventedfrom scattering due to the second gas flow and from flowing outside ofthe hybrid inflator 100.

An amount of the second gas generating agent 134 can be equal to, largeror smaller than an amount of the first gas generating agent 124, andshapes and compositions of the first and second gas generating agentsmay be the same or different from each other. Volumes of the first gasgenerating chamber 120 and the second gas generating chamber 130 may bethe same or different from each other, and the volumes can be adjustedby the first partition wall 126 and the second partition wall 136.

As described above, the flame transferring means chamber 110 is incommunication with the first gas generating chamber 120, the first gasgenerating chamber 120 is in communication with the inflator housing102, and further, the second gas generating chamber 130 is incommunication with the inflator housing 102. With this structure,pressures in the flame transferring means chamber 110, the first gasgenerating chamber 120, and the second gas generating chamber 130 aremaintained at high level, i.e., at the same level as the pressure in theinflator housing 102 (inner space 103).

The first gas generating chamber 120 and the second gas generatingchamber 130 are disposed adjacent to each other in series in thelongitudinal direction of the inflator housing 102. By disposing thesechambers in series in this manner, even when the gas generating chamberis divided into two, the entire size of the hybrid inflator can be madecompact, and weight increase can be limited.

The first gas generating chamber 120 and the second gas generatingchamber 130 have independent passages through which gases generated bythe respective combustion of the first gas generating agent 124 and thesecond gas generating agent 134 flow into the inflator housing 102. Thatis, the gas generated in the first gas generating chamber 120 flows intothe inflator housing 102 from the first communication holes 125, and thegas generated in the second gas generating chamber 130 flows into theinflator housing 102 from the second communication holes 135.

The first and second gas generating chambers 120, 130 are disposed insuch a manner that, when the gas generated in the first gas generatingchamber 120 flows towards a diffuser port 182 inside the inflatorhousing 102 after passing through the first communication holes 125 ofan inflow passage, the second communication holes 135 which is an inflowpassage of the second gas generating chamber 130 is located in thereverse direction of the gas flowing direction with respect to the firstcommunication holes 125 which is an inflow passage of the first gasgenerating chamber 120.

By disposing the first and second gas generating chambers 120, 130 inthis manner, combustion in the first gas generating chamber 120 does notaffect the one in the second gas generating chamber 130. Such a layoutis effective in that combustion in the first gas generating chamber 120does not affect the one in the second gas generating chamber 130 whenthe pressurized medium does not contain oxygen. The order of disposingthe first gas generating chamber 120 and the second gas generatingchamber 130 may be reversed.

An ignition means chamber 114 formed in the boss 145 includes the firstand second ignition means chambers 115, 141. The first ignition meanschamber 115 accommodates the first igniter 117, and the second ignitionmeans chamber 141 accommodates the second igniter 140. The first andsecond ignition means chambers can be disposed in parallel, adjacent toeach other in the widthwise direction of the inflator housing 102.

The first igniter 117 and the second igniter 140 are mounted on the boss145 through an igniter collar 143. The boss 145 is fixed to the inflatorhousing 102 at a connecting portion 146 by welding or the like.

An adapter 170 is connected in extension of the flame transferring meanschamber 110. A projectile 175 having the illustrated shape for rupturinga main rupturable disc 178 at the time of activation is mounted, throughan O-ring 172, to an opening that brings the flame transferring meanschamber 110 and the adapter 170 into communication with each other suchthat the projectile 175 straddles the flame transferring means chamber110 and the adapter 170. A tip of the projectile 175 is located in theinner space 176 of the adapter 170. The inner space 176 and the innerspace 103 of the inflator housing 102 are in communication only througha required number of gas inflow holes 166 provided on a surface of theadapter 170 facing an inner surface of the housing 105. A gas flow path105 a is formed by the inner surface of the housing 105 and an outersurface of the adapter 170. Therefore, the pressurized medium in theinner space 103 flows into the gas inflow holes 166 inevitably throughthe gas flow path 105 a at the time of activation.

The diffuser 180 is connected to one end of the inflator housing 102.The diffuser 180 is fixed at its connecting portion 181 by welding. Themain rupturable disc 178, as the main closing means, is mounted to theend of the diffuser 180 facing the projectile 175 in order to block amoving path of the pressurized medium towards the diffuser port 182before activation. Therefore, before activation, a gas inflow space 150and the inner space 103 of the inflator housing 102 are completelyisolated from each other and thus, transmittance of the pressurizedmedium is blocked.

The diffuser 180 is provided at the other end with a plurality ofdiffuser ports 182 for sending the pressurized medium to the air bag andalso with a diffuser screen 186 for removing fine particles. A stud bolt190 for connecting the diffuser 180 with the air bag module is fixed tothe outer face of the diffuser 180.

In the hybrid inflator 100, it is preferable that the above-describedconstituent elements are arranged symmetrically in the widthwisedirection with respect to the center axis (shown as the chain line inFIG. 1), but some or all of the constituent elements may be arrangedeccentrically with respect to the center axis.

In the hybrid inflator of the present invention, the arrangement of thefirst and second gas generating chambers can be varied as describedbelow.

For example, the first gas generating chamber 120 and the second gasgenerating chamber 130 can be arranged to face each other on theopposite sides inside the inflator housing 102. In this case, thepressurized medium is charged into the space between the first gasgenerating chamber 120 and the second gas generating chamber 130.

Further, for example, in the inflator housing 120, the first gasgenerating chamber 120 (or the second gas generating chamber 130) maysurround the flame transferring means chamber 110, and the second gasgenerating chamber 130 (or the first gas generating chamber 120) maysurround the first gas generating chamber 120.

The air bag system of the present invention comprises activation-signaloutputting means including an impact sensor and a control unit, and amodule case in which the hybrid inflator 100 and an air bag areaccommodated. The hybrid inflator 100 is connected to theactivation-signal outputting means (the impact sensor and the controlunit) on the side of the first igniter 117 and the second igniter 140,and the hybrid inflator 100 is connected and fixed by screwing the studbolt 190 into the module case in which the air bag is mounted. In theair bag system having such a structure, it is possible to adjust anamount of gas generated in accordance with a degree of the impact, andto adjust the inflating speed of the air bag by appropriately settingthe output condition of the activation signal in the activation-signaloutputting means.

Next, the operation of the hybrid inflator 100 will be explained withreference to FIG. 1. Before the hybrid inflator 100 is activated, thepressurized medium stored in the inflator housing 102 under a highpressure exists in the first gas generating chamber 120 and the secondgas generating chamber 130 which communicate with each other by means ofthe communication holes 125 and 135 respectively, and further exists inthe flame transferring means chamber 110 through the communication holes118, and the insides of these chambers are maintained at the same highpressure. Further, the projectile 175 is mounted to straddle between theflame transferring means chamber 110 and the inner space 176 which aremaintained at the same pressure, the malfunction is prevented.

In the event of a vehicle collision, the first igniter 117 is ignited bythe activation signal outputting means to rupture the first rupturabledisc 119 (fixed to the boss 145 defining the first communication hole113) to ignite and burn the booster agent 112 a in the flametransferring means chamber 110, thereby generating a high temperaturebooster gas. When the pressure inside the flame transferring meanschamber 110 is increased by the generated booster gas, the projectile175 pushed by this pressure moves to rupture the main rupturable disc178 with the sharp tip of the projectile 175. At that time, a portion ofthe booster gas flows into the gas inflow space 150 due to the ruptureof the main rupturable disc 178.

Most of the booster gas flows into the first gas generating chamber 120through the flame-transferring holes 118 to ignite and burn the firstgas generating agent 124, and a desired amount of a high temperaturecombustion gas (corresponding to the charged amount of first gasgenerating agent 124) is generated. At that time, since the pressurizedmedium has flowed into the first gas generating chamber 120 so that thischamber 120 has been maintained at a high pressure, the combustion ofthe first gas generating agent 124 is stable. Since the flametransferring means chamber 110, the first gas generating chamber 120,and the second gas generating chamber 130 are partitioned from eachother by a cylindrical housing 111 and a second partition wall 136, thesecond gas generating agent 134 is not ignited and burned. Because ofthe arrangement of the first communication hole 125 of the first gasgenerating chamber 120 and the second communication holes 135 of thesecond gas generating chamber 130, the second gas generating agent 134is not ignited nor burnt by the combustion of the first gas generatingagent 124.

Thereafter, since the high temperature combustion gas flows through thefirst communication hole 125 into the inflator housing 102 to increasethe pressure therein, the further pressurized medium flows into the gasinflow space 150 through the ruptured main rupturable disc 178. Thefurther pressurized medium which has flowed into the gas inflow space150 in this manner is ejected from the diffuser port 182 after passingthrough the diffuser screen 186 and then, inflates the air bag mountedin the air bag module.

The second igniter 140 is ignited by the activation signal outputtingmeans simultaneously or slightly (about 10 to 40 ms) after the firstigniter 134 is activated, and the second rupturable disc 139 (fixed tothe boss 145 defining the second communication passage 133) is rupturedto ignite and burn the booster agent 112 b, and then, the second gasgenerating agent 134 in the second gas generating chamber 130 is ignitedto generate the desired amount of a high temperature combustion gas(corresponding to the charged amount of the second gas generating agent134). At that time, since the pressurized medium already exists in thesecond gas generating chamber 130 and this chamber 130 has beenmaintained at high pressure, the combustion state of the second gasgenerating agent 134 is stable. In this case, in order to ignite andburn the second gas generating agents 134, only the second igniter 140is used and a booster can be omitted.

Further, as shown in FIGS. 1 and 3, since the second igniter 140 isdisposed distantly and differently in the radial direction from thesecond communication holes 135, the second gas generating agent 134 inthe second gas generating chamber 130 is uniformly burned. For example,if the second communication holes 135 is disposed near the secondigniter 140, a portion of the second gas generating agent 134 near thesecond igniter 140 is smoothly burned, but the other portion of thesecond gas generating agent 134 located farther away from the secondcommunication holes 135 is prone to be burned in some cases.

The high temperature combustion gas generated by the combustion of thesecond gas generating agent 134 flows into the inflator housing 102through the second communication holes 135 to increase a pressuretherein, the remaining pressurized medium flows into the gas inflowspace 150 through the ruptured main rupturable disc 178, and is ejectedfrom the diffuser port 182 to further inflate the air bag.

The hybrid inflator described above generates the combustion gas in twostages. The first gas generating chamber 120 can act to inhibit aninflating action of the air bag from lagging at a vehicle collision, andthe second gas generating chamber 130 enables to discharge thepressurized medium completely from the inflator housing 102 and to makethe air bag inflated immediately up to the satisfying safety level.

Additionally, since two gas generating chambers are provided, thishybrid inflator can also be adapted to a mode of embodiment in which acombustion gas is generated only in the first gas generating chamber 120alone, a mode of embodiment in which a combustion gas is generated inthe first and second gas generating chambers 120 and 130 simultaneously,and a mode of embodiment in which an interval between the timing ofgenerating a combustion gas in the first gas generating chamber 120 andthat of generating a combustion gas in the second gas generating chamber130 is controlled in a desired manner.

EXAMPLE

The present invention is described more specifically below by referringto Example. However, the present invention is not limited thereto. Bythe way, the gas generating agent described below is shaped in asingle-perforated cylinder having the outer diameter of 5.4 mm, theinner diameter of 0.7 mm and the length of 5 mm.

Example 1

A dual-type hybrid inflator 100 of the embodiment shown in FIG. 1 wasproduced. The details are as follows:

The inflator housing 102 was produced by using high tensile strengthsteels (a tensile strength of 90 kg/mm²). As the pressurized medium, 2.6mol (100 g) of a mixed gas comprising argon and helium [Ar:He=96:4(molar ratio)] was used (the internal pressure of 32,000 kPa). As thegas generating agent, 20 g of a composition comprising nitroguanidine,strontium nitrate, carboxymethylcellulose and acid clay (34:50:9:7) wasused (A/B=7.2/2.8) for each of the first and second gas generatingchambers (40 g in total, which corresponds to 1.0 mol of the generatedgas). A weight ratio (X/Y) between the pressurized medium and the gasgenerating agent was 2.5. Accordingly, at the activation, totally 3.6moles of the gas could be used, and the total weight of the pressurizedmedium and the gas generating agent before the activation was 140 g. Inthis case, the pressure index (n) was 0.6.

The hybrid inflator 100 of the above structure had 54 mm of the diameterand 156 mm of the length (the length not including the stud bolt whoselength was 20 mm). The thickness of the inflator housing 102 was 2.5 mm,and the total weight of the inflator was 1200 g. When this hybridinflator 100 was activated by simultaneously igniting the first andsecond igniters, the internal pressure of the inflator housing 102 was48,000 kPa.

1. A hybrid inflator for an inflating-type safety system of a vehicleprovided with an air bag, comprising: an inflator housing containing apressurized medium including an inert gas; a gas generator provided insaid inflator housing, said gas generator including, a gas generatorhousing provided with a plurality of communication holes, a gasgenerating chamber in which a gas generating agent is accommodated, saidgas generating chamber and said inflator housing being in communicationwith each other through said communication holes, and each of saidcommunication holes provided in said gas generator housing having such asize that a combustion gas generated in said gas generating chamber ispermitted to flow out into said inflator housing while preventing thegas generating agent from moving out of said gas generating chamber; andan ignition means chamber having an ignition means connected to said gasgenerator, wherein the hybrid inflator satisfies at least onerequirement selected from the following requirements (1) to (3): (1) Amolar ratio between an amount (A mol) of the pressurized medium and anamount (B mol) of a gas generated due to combustion of the gasgenerating agent is 8/2 to 1/9; (2) A weight ratio (X/Y) of the weight(X) of the pressurized medium to the weight (Y) of the gas generatingagent is 0.1 to 7; and (3) A pressure index determined by the followingformula: rb=αP^(n) (wherein, rb: burning rate, α: coefficient, P:pressure, n: pressure index), at the combustion of the gas generatingagent, is smaller than 0.8.
 2. A hybrid inflator for an inflating-typesafety system of a vehicle provided with an air bag, comprising: aninflator housing containing a pressurized medium including an inert gas;a gas generator provided in said inflator housing, said gas generatorincluding, a gas generator housing having a plurality of first andsecond communication holes, first and second gas generating chamberseach containing a gas generating agent, said first gas generatingchamber and said inflator housing being in communication with each otherthrough said first communication holes, and said second gas generatingchamber and said inflator housing being in communication with each otherthrough said second communication holes, and said first and secondcommunication holes having such a size that a combustion gas generatedin said first and second gas generating chambers are permitted to flowout into said inflator housing while preventing the gas generating agentfrom moving out of said first and second gas generating chambers; and anignition means chamber having ignition means connected to said gasgenerator, wherein the hybrid inflator satisfies at least onerequirement selected from the following requirements (1) to (3): (1) Amolar ratio between an amount (A mol) of the pressurized medium and anamount (B mol) of a gas generated due to combustion of the gasgenerating agent is 8/2 to 1/9; (2) A weight ratio (X/Y) of the weight(X) of the pressurized medium to the weight (Y) of the gas generatingagent is 0.1 to 7; and (3) A pressure index determined by the followingformula: rb=αP^(n) (wherein, rb: burning rate, α: coefficient, P:pressure, n: pressure index), at the combustion of the gas generatingagent, is smaller than 0.8.
 3. A hybrid inflator for an inflating-typesafety system of a vehicle provided with an air bag, comprising: aninflator housing containing a pressurized medium including an inert gas;a gas generator provided in said inflator housing, said gas generatorincluding, a gas generator housing having a plurality of first andsecond communication holes, first and second gas generating chamberseach having a gas generating agent, a first ignition means chamberhaving first ignition means connected to a first gas generating chamber,a second ignition means chamber having second ignition means connectedto a second gas generating chamber, said first gas generating chamberand said inflator housing being in communication with each other throughsaid first communication holes, said second gas generating chamber andsaid inflator housing being in communication with each other throughsaid second communication holes, said first and second communicationholes having such a size that a combustion gas generated in said firstand second gas generating chambers are permitted to flow out into saidinflator housing while preventing the gas generating agent from movingout of said first and second gas generating chambers, and said secondcommunication holes being disposed at a distance from said secondignition means in one of the widthwise direction and the longitudinaldirection of said inflator housing; and an ignition means chamber havingan ignition means connected to said gas generator, wherein the hybridinflator satisfies at least one requirement selected from the followingrequirements (1) to (3): (1) A molar ratio between an amount (A mol) ofthe pressurized medium and an amount (B mol) of a gas generated due tocombustion of the gas generating agent is 8/2 to 1/9; (2) A weight ratio(X/Y) of the weight (X) of the pressurized medium to the weight (Y) ofthe gas generating agent is 0.1 to 7; and (3) A pressure indexdetermined by the following formula: rb=αP^(n) (wherein, rb: burningrate, α: coefficient, P: pressure, n: pressure index), at the combustionof the gas generating agent, is smaller than 0.8.
 4. A hybrid inflatoras claimed in claim 1, wherein the plurality of communication holes arenot covered with a screen.
 5. A hybrid inflator as claimed in claim 1,wherein said gas generating agent is in contact with the plurality ofcommunication holes provided in said gas generator housing.
 6. A hybridinflator as claimed in claim 1, wherein the plurality of communicationholes provided in said gas generator housing have the same holediameters.
 7. A hybrid inflator as claimed in claim 1, wherein theplurality of communication holes provided in said gas generator housinghave hole diameters in a range of 0.5 to 3 mm.
 8. A hybrid inflator asclaimed in claim 1, wherein the total number of the plurality ofcommunication holes provided in said gas generator housing is 100 to600.
 9. A hybrid inflator as claimed in claim 1, wherein the total openarea of the plurality of communication holes provided in said gasgenerator housing is 100 to 600 mm².
 10. A hybrid inflator as claimed inclaim 1, wherein the plurality of communication holes provided in saidgas generator housing are disposed in a plurality of lines in thelongitudinal direction of said gas generator housing and in a pluralityof the lines in the circumferential direction.
 11. An air bag systemcomprising: activation-signal outputting means including an impactsensor and a control unit; and a module case in which a hybrid inflatoras claimed in claim 1 and an air bag are accommodated.
 12. A hybridinflator as claimed in claim 2 or 3, wherein, in the first communicationholes and the second communication holes provided in said gas generatorhousing, the total number of said first communication holes is 50 to300, and the total number of said second communication holes is 50 to300.
 13. A hybrid inflator as claimed in claim 3, wherein, in the firstcommunication holes and the second communication holes provided in saidgas generator housing, the first communication holes are disposed in aplurality of the lines in the longitudinal direction of said gasgenerator housing and on the entire surface in the circumferentialdirection, and the second communication holes are disposed in aplurality of the lines in the longitudinal direction of said gasgenerator housing and on a half or less of the surface in thecircumferential direction.
 14. A hybrid inflator as claimed in claim 3or 13, wherein said gas generator further includes a flame transferringmeans chamber, said flame transferring means chamber is disposed inextension in the longitudinal direction of said first ignition meanschamber and is in communication with said first gas generating chamber,said second ignition means connected to said second gas generatingchamber is disposed eccentrically with respect to the center axis ofsaid inflator housing in the longitudinal direction.
 15. A hybridinflator as claimed in claim 3, wherein said first and second ignitionmeans chambers are disposed adjacent to each other as well as inparallel in the widthwise direction of said inflator housing, said firstignition means chamber is disposed on the center axis in thelongitudinal direction of said inflator housing.
 16. A hybrid inflatoras claimed in claim 2 or 15, wherein said first and second gasgenerating chambers have independent inflow paths for gases generatedtherein towards said inflator housing.
 17. A hybrid inflator as claimedin claims 2 or 3, wherein at least one of the first communication holesand the second communication holes are not covered with a screen.
 18. Ahybrid inflator as claimed in claim 2, wherein at least a portion of thefirst communication holes and the second communication holes provided insaid gas generator housing are formed in different directions in thewidthwise direction of said inflator housing.
 19. A hybrid inflator asclaimed in claim 2, wherein said first and second gas generatingchambers are disposed adjacent to each other in series in thelongitudinal direction of said inflator housing.
 20. A hybrid inflatoras claimed in claim 2, wherein said first and second gas generatingchambers are disposed to face each other in series in the longitudinaldirection of said inflator housing.
 21. A hybrid inflator as claimed inclaim 2, wherein said first and second gas generating chambers aredisposed in parallel, adjacent to each other or at a distance from eachother in the widthwise direction of said inflator housing.
 22. A hybridinflator for an inflating-type safety system of a vehicle, comprising:an inflator housing that accommodates a pressurized medium; a firsthousing provided in the inflator housing and containing a first gasgenerating agent, the first housing having a first communication holethat allows the pressurized medium and gas generated in the firsthousing to flow therethrough while retaining the first gas generatingagent in the first housing; a second housing provided in the inflatorhousing and containing a second gas generating agent, the second housinghaving a second communication hole that allows the pressurized mediumand gas generated in the second housing to flow therethrough whileretaining the second gas generating agent in the second housing; and apartition wall provided between the first housing and the secondhousing.
 23. The hybrid inflator as claimed in claim 22, wherein thefirst communication hole and the second communication hole are notcovered.
 24. A hybrid inflator as claimed in claim 22, wherein the firstgas generating agent makes contact with the first communication hole andthe second gas generating agent makes contact with the secondcommunication hole.
 25. The hybrid inflator as claimed in claim 22,further comprising: a first ignition unit that ignites the first gasgenerating agent; and flame transferring means, extending inside thefirst housing along a longitudinal direction of the housing, fortransferring flame generated by the first ignition unit to the first gasgenerating agent.
 26. The hybrid inflator as claimed in claim 22,further comprising: a second ignition unit that ignites the second gasgenerating agent, the second ignition unit being connected to the secondhousing such that the second ignition unit is disposed eccentricallywith respect to a center axis of the inflator housing.
 27. The hybridinflator as claimed in claim 22, wherein said first housing and thesecond housing are disposed adjacent to each other in series in alongitudinal direction of the inflator housing.
 28. The hybrid inflatoras claimed in claim 22, further comprising: a space provided inside theinflator housing and in fluid communication with the pressurized mediumaccommodating chamber.